chore(deps): update dependency typedoc to ^0.20.0

Author: renovate-bot

package.json

@@ -47,7 +47,7 @@
     "ts-jest": "^24.3.0",
     "tslint": "^5.12.0",
     "tslint-config-prettier": "^1.17.0",
-    "typedoc": "^0.15.0",
+    "typedoc": "^0.20.0",
     "typescript": "^3.2.4"
   },
   "publishConfig": {